Maggio E T, Ullman E F
Biochim Biophys Acta. 1978 Feb 10;522(2):284-90. doi: 10.1016/0005-2744(78)90062-1.
The inhibition of pig heart mitochondrial malate dehydrogenase (L-malate: NAD+ oxidoreductase, EC 1.1.1.37) by the thyroxine and structurally related compounds was studied to resolve a longstanding question about the exact nature of the inhibition. Thyroxine, in freshly prepared solution, was found to be a "pure" competitive inhibitor relative to the nucleotide cofactor. Upon standing in diffuse daylight, solutions of thyroxine showed increased ability to inhibit the enzyme, presumably as a result of oxidation of enzyme sulfhydryl groups by free iodine that is released photochemically. This behavior probably accounts for earlier reports of irreversible inactivation by thyroxine. Comment is made on the implications of these findings to the mechanism of thyroid hormmone action.
研究了甲状腺素及结构相关化合物对猪心脏线粒体苹果酸脱氢酶（L-苹果酸：NAD+氧化还原酶，EC 1.1.1.37）的抑制作用，以解决一个长期存在的关于抑制的确切性质的问题。相对于核苷酸辅因子，新鲜制备溶液中的甲状腺素被发现是一种“纯粹”的竞争性抑制剂。在漫射日光下放置时，甲状腺素溶液抑制该酶的能力增强，这可能是由于光化学释放的游离碘氧化酶的巯基所致。这种行为可能解释了早期关于甲状腺素不可逆失活的报道。对这些发现对甲状腺激素作用机制的影响进行了评论。
